1. Field of the Invention
The invention relates to biologically compatible polyaspartic acid derivatives and their application primarily for pharmaceutical and food preparations.
2. Description of the Background
Polymeric substances are used on a large scale in both the pharmaceutical technology and food technology. In these applications these substances are in themselves not drugs or foods but rather are indispensable for specific applications of the active ingredients or for, e.g., the special processing of foods.
Polymeric, film-forming substances are, for example, used to improve the handling of pharmaceutical preparations, to improve their storage stability and, above all, to influence the rate of release of the active substances during their medicinal application. Synthetic polymers and chemically modified natural substances such as polyethylene glycol, polyvinylpyrrolidone, polymethacrylates, polyvinyl acetates and cellulose ester and cellulose ether are used.
A number of synthetically manufactured polypeptides already exist for special applications in medicine and pharmacy. Apart from peptides with effect-specific sequence, there are also polymers from individual amino acids such as primarily polyaspartic acid, polyglutamic acid and polylysine, and copolymerizates of monomer components on which these polyamino acids are based. These polymers have no special biological efficacies and have been proposed as plasma expanders.
Derivatives of such polyamino acids are also known and are biologically quite compatible. Thus, .alpha.-.beta.-poly(2-hydroxyethyl)-DL-aspartamide can be employed as a plasma expander (P. Neri et al., Journal of Medicinal Chemistry, 1973, Vol 16, pages 893-897). Acyl derivatives of .alpha.-.beta.-poly(2-hydroxyethyl)-DL-aspartamide and, in general, of .alpha.,.beta.-poly-(hydroxyalkyl)-DL-aspartamides are described in DE-OS 37 00 128. By building in suitable biologically inactive acyl groups the decomposition rate of these polymers can be controlled in vivo in the desired manner. Thus, they are suitable for incorporating decomposable drug implants with controlled release of the active substances. The active substances are embedded in the polymer matrix.
Soluble and biologically degradable copolymerizates from aspartic acid and/or glutamic acid units, which contain reactive groups such as, e.g., hydrazide or azide groups, for the chemical bonding of biologically active substances are known from DE-OS 36 12 102.
In order to achieve a targeted release of active substances to or in the vicinity of their sites of action, drugs are administered a multiple number of times in the form of coated tablets. All previously known polyamino acids and their derivatives have not yet been used as surface coatings for medicinal forms and also for foods despite the foreseeable advantages. This can be justified by the cost or the reason can lie in the properties of polyamino acids and their derivatives that are known to date. Thus, the prior art .alpha., .beta.-poly-(2-hydroxyethyl)-DL-aspartamide is too hydrophilic for the field of application of coatings for medicinal preparations and foodstuffs.